It is well known in the field of directional antennas, such as for example cellular communication antennas, that imprecise alignment of the antenna leads to weaker signal transmission and reception to and from the required sector by the antenna and a generally smaller coverage range. This affects the quality of the information that is being transferred, especially by 3-G cellular devices. For example, this causes lower data transfer rates and more errors and interference. For cellular companies, for example, this generally results in increased operational costs and loss of incomes. The antenna can become misaligned with the predetermined direction in which it is supposed to point due to initial inaccurate alignment, lack of accurate direction measurements during realignment to the same or a different direction, and due to multiple gradual or sudden external factors such as wind, rain and intentional or unintentional actions of people in its vicinity.
Typically, antennas are aligned by technicians who arrive to the site where the antenna is located. Prior art alignment methods mainly rely on external references having known geodetic coordinates. Considerable use is also made of magnetic compasses. According to an exemplary common practice, the alignment is carried out by a first technician who climbs the antenna tower and rotates an antenna that is pivotally attached to a typically vertical axle. A second technician directs him from the ground using binoculars with a built in compass, in order to determine the required pointing direction for the antenna.
Some most recent prior art methods and systems started to use GPS (Global Positioning System) signals. GPS positioning data signals can be used to accurately determine an azimuth direction or azimuth (the angle between any horizontal vector on the surface of the Earth and the meridian passing through the true North), by processing the longitude and latitude parameters of two different locations where GPS readings are taken and using, for example, the great circle method. Dedicated equipment or readily available computer software, like for example the GPS Utility Program, can be used to process such double GPS positioning data and provide accurate azimuth information.
U.S. Pat. No. 6,897,828 to Boucher teaches a method of aligning an antenna within a predetermined azimuth direction, by processing positioning data from at least one GPS receiver dish that is connected to the antenna and locatable at predetermined first and second positions away from the antenna. The receiver dish is used to determine an antenna azimuth and then moved towards the predetermined azimuth so as to align the antenna.
U.S. Pat. No. 7,180,471 also to Boucher describes a system and method of aligning an antenna with a predetermined azimuth direction. Positioning data, received by a GPS receiver dish locatable at predetermined first and second positions away from the antenna, is processed in conjunction with a reference tool that is connected to the GPS receiver dish and operatively coupled to at least two reference targets affixed to the antenna. The receiver dish is used to determine an antenna azimuth and then moved towards the predetermined azimuth, so as to align the antenna with the help of the reference tool and reference targets.
However, the above and other prior art systems suffer from a number of disadvantages:    1. As is well known, the direction of the Earth's magnetic North is not identical to the direction of the true North (which corresponds to the Earth's rotational axis). Thus, while a cellular network, for example, is planned on maps aligned with the direction of true North, its physical alignment is currently carried out by a magnetic compass, which shows the magnetic North. This introduces an inherent error into the alignment process, which is further difficult to correct because the Earth's magnetic field is non-uniform and its direction can vary by many degrees at different locations on the Earth's surface.    2. The common practice of using compasses is further problematic due to the potentially strong electromagnetic fields near antenna towers and could deteriorate the reading of a compass. As a result of this interference as well as the misalignment of the magnetic North with the true North, the typical antenna misalignment due to alignment by technicians using magnetic compasses is in the range of 5-20 degrees, depending on the skill of the technicians who carry out the alignment. And the total misalignment of an antenna is typically in the 10-30 degree range.    3. The use of computerized engineering design tools requires precise network parameters (location, altitude, type and direction of each antenna and other data). Today, for cellular networks for example, the initially inaccurate parameters are manually fed into the computer, which causes faults and lack of live, or at least daily, updates. In time, this situation leads to considerable discrepancies between the computer records and the actual antenna pointing directions in field, thus making it nearly impossible for a communication or cellular engineer to optimally design the communication network, and might require extra redundancy in the form of more antenna towers for example, resulting in higher costs.    4. Inaccuracies in the pointing directions of antennas in the field are likely to lead to poor reception and transmission coverage. While these problems were less critical in the past, they become very critical factors for modern day communications which increasingly use massive wide-band digital data transmission, such as multimedia content and Internet browsing. Poor coverage leads not only to interference, but also to reduced data transfer rates and errors. This further translates into higher operating costs and loss of incomes for communications and cellular companies and the end-users.    5. Due to environmental issues related to the electromagnetic radiation emitted by the antennas, especially in the more concentrated form for directional antennas, such as cellular antennas, every field deployed antenna receives a separate permit for its installation and operation. Inherent inaccuracies in an antennas pointing direction reduce the range of possible installation sites and locations, and pointing direction inaccuracies during operation of an antenna can affect its permit and cause general legal problems to the transmission site and/or communication companies.    6. Solutions involving mounting complex systems proximate to antenna/s that can find its azimuth are usually impractical and involve very high costs and other complications.
It is therefore an object of the present invention to provide a system and method for accurately directing antennas, and which overcomes the problems associated with the prior art.
It is an object of the present invention to enable accurate direction of antennas.
It is another object of the present invention to enable accurate direction of antennas that is not susceptible to errors in the calibration process due to the Earth's non-uniform magnetic field.
It is yet another object of the present invention to enable accurate direction of antennas that is not susceptible to the electromagnetic interference that the antennas often cause.
It is a further object of the present invention to enable better and simpler engineering and design of antenna based communications networks.
It is an optional object of the present invention to enable simpler and accurate subsequent redirections of an antenna after only one uncomplicated initial calibration procedure.
It is another optional object of the present invention to enable accurate and simple monitoring of the pointing direction of an antenna.
It is a further object of the present invention to reduce costs, boost performance, reduce negative environmental impact and generally improve the operation of antenna based communication networks.
Other objects and advantages of the invention will become apparent as the description proceeds.